This happened at Gutersloh a long time ago to a young pilot (now recently deceased) who was showing a young lady ( possibly a "tooley" from Sundern school ) a Hunter in the hangar. Young lady, sitting in the cockpit whilst young pilot stands on ladder and leans into cockpit points to various exciting controls. "And what happens if I pull this knob?" whereupon she does so. Our brave young pilot just manage to lean back a little before the canopy jettison rail struck him a glancing blow knocking him off the ladder.
But this was a long time ago and apart from wounded pride and an extended period of orderly officer nothing more was said. Couldn't happen now !